


Fireflys

by GasterKat



Category: Undertale (Video Game)
Genre: Fluff and Smut, M/M
Language: English
Status: In-Progress
Published: 2020-06-15
Updated: 2020-09-27
Packaged: 2021-03-03 21:01:35
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 2,733
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24732010
Author URL: https://archiveofourown.org/users/GasterKat/pseuds/GasterKat
Summary: This is trash. Gaster x Sans
Relationships: W. D. Gaster/Sans
Comments: 7
Kudos: 26





	1. Shelter

**Author's Note:**

> Trash

**Summary for the Chapter:**

> itz trash LMAO

January 1st, 19XX, The new year: 

The city was a live with talk and laughter, even at one in the morning. Humans and Monsters alike roamed and celebrated. Monsters were kinder by nature and tended to stay to close-knitted clique while Humans made friends and got drunk out of their minds. However, one Monster was on his own with only his baby brother for company. Instead of partying and having fun, this monster was walking through town with his brother in his arms. 

“Shhh~ It’s ok Papy you're ok.” The monster shushed as his little one cried. He knew Papyrus was hungry but he couldn’t do anything about it. He had to find a safe place to stay before sunrise or him and Papy would be in a dangerous situation. Him having 1 HP made him an easy target and his brother was defenseless so if they got attacked, they were fucked. 

“Snans!” Papyrus whimpered over and over as he looked over His brothers back. His big brother looked down at his small frame and sighed, “Fo! Fo!” 

“I know baby bro but we have to find somewhere safe.” He muttered as he pushed through a crowd of people, “Just wait a little longer ok buddy? I know your cold and hungry but give me a minute ok?” 

“K!” Papy smiled this soft, reluctant smile before burrowing deeper in the blanket he was wrapped in. Then he was grabbed, boney hands pulling him out of the way of a knife. His eye sockets widened as Sans ripped his arm out of the being's grasp and his now free hand shot upwards as he activated his magic. Bones the size of a man and even thicker burst from the ground as passerby's ran for their life. The culprit of the attack dogged the bones and lunged at the small skeleton. Sans jumped as high as he could and summoned a Gaster Blaster. The animalistic skull burst through the ground beneath the skeleton brothers and shot through the air with them on its back. Just as the blaster was about to fire, floating hands surrounded by a purple haze shot to the attacker and pinned them to the ground. The culprit quickly struggled free and ran away before he could be properly caught. 

Sans was huffing as the skull dropped him to the ground and disappeared. As he turned to thank whoever helped him he froze. 

“Why hello there! I’m Dr. W. D. Gaster.”


	2. A kind offer

**Summary for the Chapter:**

> much better trash that was written at two times making it weird!

I decided to change Papy’s age for the sake of the story so sorry about the last chapter not making as much sense now! 

-GasterKat 

1:34 AM: 

“Why hello there! I’m Dr. W. D. Gaster.” The man said with slightly surprised eyes. 

“Sorry for staring but it’s not every day that you see another skeleton monster and even rarer to see one so skilled in combat!” 

Sans had learned to be wary of strangers since childhood so he was wary of this new comer. Instinctively he narrowed his eyes and turned so Papyrus was in an easier position to protect the small child. He studied the man carefully taking in every little detail no matter how small. The man had to easily be almost 30, not too far from Sans’s almost 19 but he was painfully aware of how little that mattered when you had low HP. Plus Papyrus was only 8 and was scared to hurt a bug much less a monster so Sans had to protect him at all costs. 

“If ya wanna know how I'm so good at fighting it’s cuz I have ta be.” He growled out his perma-smile tilting downwards in what could only be considered a frown. The skeleton was shocked at how fast his mood changed. Before he could say anything the smaller whimpered and when they looked at him his eyes were filled with tears. His face was flushed a deep orange and his top teeth were nibbling on his bottom. Sans immediately took charge and sat down putting Papyrus in his lap, whispering comporting words where his ear would be. 

Gaster watched this with fascination, he thought it cute for the skeleton to be so protective and caring for his obviously younger brother. Maybe it was his sister? It was seemingly impossible to tell skeletons gender with just looking at them. The only reason he even knew the older was a boy was because of his clothes and voice but the smaller was wearing clothes that could be for either gender and he had yet to hear the young boy speak. 

When Papy was finally calmed down Sans looked at the so called ‘Gaster’ with mistrust apparent in his eye lights. Gaster looked back at the child with an interested expression. 

“Well your mom certainly won’t be happy if you are out to long so it would be best if you ran along now!” Gaster offered smiling down at the children before offering the oldest a hand. “If you wish I could accompany you to where your parents are.” 

“No thanks.” The taller snapped tensing up at the mere mention of parents. He stood on his own before hoisting the smaller with him. “Come on Paps we gotta find a place for the night, k buddy?” 

“Ok! Will we get food?” The little one asked innocently. Gaster had frozen. What did they mean ‘find a place for the night’? And why was a child asking if they were going to have food? 

“Sure, I’ll see if I have enough Gill ok? Now say bye to the nice man and let’s go.” The older said sweat-dropping as he pointed at Gaster. 

“Bye bye nice man!” The small giggled looking at Gaster with adoration apparent in his eyes. But before they could leave Gaster grabbed the oldest stopping him in his tracks. 

“Do you want to stay the night at my house?”


	3. Hot coco is necessary

**Summary for the Chapter:**

> Sorry it took so long. I ran out of ideas TwT

“Do you want to stay the night at my house?” Gaster asked as he gripped the skeletons arm. Said skeleton looked at him with surprise and mistrust written all over his skull. He yanked his arm from Gaster’s grip and looked at Papy. Papy gave him a big smile and a thumbs up. 

“Are you sure buddy? We barely know the guy and I’ll find us somewhere safe if we don’t.” Sans desperately asked hoping that Papy would say no. 

“Hmmm... Mister?” Papyrus asked turning to the taller skeleton. 

“Yes child?” 

“Will there be beds and blankets and food? Oh! Will I get to have hot coco!? Will the blankets be fluffy!? Will I get to have Fluffy Bunny read to me!? Will-” Papy said getting more and more excited with each word. 

“Hey! Hey! I can only answer so many questions! Yes, there will food and beds and blankets. Yes, I have fluffy blankets. I don’t know if I have hot coco but if I do then yes. If you have Fluffy Bunny, I can read it to you if you wish. Now anything else?” Gaster hastily replied cutting the child off before he could get too far. 

“Will it be safe?” Papyrus mumbled hiding his mouth in his scarf. Gaster could barely hear him but he when pieced it all together, he smiled the warmest smile Sans had ever seen and told Papy that he hoped his house was safe but that no place was perfect and that neither was he. 

“Sans?” Papy smiled turning to his older brother. 

“Yeah baby bro?” Sans replied crouching so he was at his brother's height. 

“Can we?” Papy pleaded as he stared up at Sans with his best puppy dog eyes. Sans knew as much as he wanted to, he couldn’t say no to that face. He stood up and look at Gaster with challenging eyes then look back down at Papy. 

“One night got it? Please don’t cause to much trouble for the poor man or were going to leave ok?” Sans agreed sternly as Papy bounced up and down. 

“I will be the best! I am the Great Papyrus after all!” Papy almost yelled as he ran around Sans and Gaster in his excitement. 

“Well I guess that settles it! Would you like to go there now?” Gaster chuckled as his eyelights grew brighter at Papyruses antics. 

“Hold on I have to grab something. Papy wanna get Fluffy Bunny!” He said to Gaster before turning and shouting at Papy who had ran down the street a little ways. 

“REALLY?!” Papyrus shouted in excitement. 

“Yup and were gonna take one of my shortcuts too!” Sans laughed as Papyrus raced down the street towards them. Papy grabbed one of Sans’s hands in both of his as his eye sockets light up. They suddenly disappeared right before Gaster’s eyes. He whipped around and searched for where they could have gone but they were nowhere to be seen. He had started panicking when they popped up out of thin air again. 

“Does that satisfy your teleportation crave for a little?” Sans said looking at his brother with questioning eyes. 

“Yep! But next time can we not do it two times in a row so quickly please?” Papy asked looking slightly tired from all that. During the whole thing Gaster was just staring at them like they had grown a second head. Sans quickly glanced at Gaster before turning to him. 

“I’m not gonna answer anything, ok? You probably are only gonna see that one time and that one was for a very good reason.” Sans said as he glared at the skeleton. 

“Alright...” Gaster sighed rubbing his eyes sockets, “Now are you ready to go?” 

“Yes! Let’s go! Hurry!” Papyrus shouted as he jumped and shook with excitement. 

“It’s just down the street if you want to get there first. It’s the grey house!” Gaster shouted after Papyrus as he shot down the street. Turning back to Sans, Gaster motioned in the direction of his house and said, “Shall we go before your brother breaks something?” 

“Sure bud but don’t expect your house to be intact tomorrow.” Sans replied as he lazily walked down the street, “See ya there old man.” 

“What interesting siblings...” Gaster muttered before jogging to catch back up with Sans.


	4. fluffy feeling

**Summary for the Chapter:**

> I wanna die!:'( Sorry about how late this was! School started and I have a boyfriend now so between those 2 things i've been hella tired. Enough worthless excuses, hope you enjoy the very late and terrible chapter!

**Notes for the Chapter:**

> Love you guys!!!!!!!

Sans’s POV: 

When I had got to the house it seemed baren. Cold grey walls and a light purple trim made up the outside making it seem dull. There were no decorations, no pretty paint, and no life what so ever. That was until I stepped carefully into the house that I saw what I could only describe as heaven. 

A soft rug was laying under a light brown coffee table with a couch placed under a hilarious picture of what looked like a stylized bone on a green and yellow background I was so busy thinking of all the pun opportunities that I almost tripped on a little ledge that lead to that plush carpet. I saw Gaster, who had somehow gotten ahead of me, take his shoes off and place them in a convenient little tray made for shoes. 

Back to 2nd person because I'm horrible at writing 1st: 

Gaster had to choke back a chuckle at how entrapped in Sans was in his carpet and painting that he nearly tripped on the little bit of a rise that lead into his living room like Sans. While Sans was taking off his frankly disgusting shoes, Papyrus was running around the living room screeching like a child on Gyptmas. Now that he thought about it was the fourth of July so Gyptmas wasn’t that far of a stretch. 

Now that Sans was finally done getting his shoes off (seriously how did he even get them on?) Gaster was ready to show the boys their room for the night and find some hot coco. 

“Excuse me?” Gaster asked as he waited for Papy to stop trying to become the world's first skeleton tornado and settle down enough to be able to speak. When Papyrus was done with his tornado tendencies, Gaster asked the boys to sit on the couch as he was going to explain the rules. Sans immediately started literally dragging Papy to the couch as Gaster stood there awkwardly. 

“Ok, I have only two rules, no going into the lab and if I'm asleep then no loud noises. Oh, and I might have to go buy hot coco so I may be gone for five to ten minutes unless you wish to come with me.” Gaster stated as he looked at the ceiling to help him recite the rules without weirding out the ‘children’ sitting on his couch before looking down when he recalled the hot coco. 

‘I need to check the kitchen for coco. If I don’t have any then a quick trip to the store down the street should fix it. I only have one bedroom so I’ll have to sleep on the couch. I have to be out of the house by 7 so I’ll have to hope that they wake up and not destroy anything. If-’ Unknown to Gaster he had been mumbling the entire time and a hyper Papyrus had already gone to the kitchen and started looking for the coco. Gaster’s monolog was interrupted by Sans. 

“Yo, old man. Paps is in the kitchen if you want to keep your food, I would suggest hurrying over there with him.” When Gaster looked at the kitchen he saw that Papy was indeed ravasing his once nice and orderly kitchen. Gaster took off without a second thought, asking Papyrus to please stop raiding his kitchen all the way. Sans just looked after them while draped lazily across the couch. 

Contrary to what anyone would think Sans was still on edge. Sans didn’t know it but while Papyrus was oblivious Gaster was smarter than that. It would be ridiculous for someone in Sans’s position to relax so Gaster knew that it was an act. That and there were little hints as to how tense he really was. Because of magic a skeleton’s clothes mimic how their ecto-body loosely as to help clothes stay on. This type of magic is taught as early as possible and will be subconsciously used most of a skeleton's life. Sans had mastered this at only one so his skill at this type of magic was surprisingly good for his age and the little tells that were there were more noticeable than a normal skeleton. 

“Since I don’t have coco would either of you boys want to come with me to the store?” Gaster asked as he walked out of the now messy kitchen. 

“Me! Me!” Papyrus giggled as he zoomed over to the couch and flopped on Sans. 

“If Paps is going I might as well.” Sans responded as he lightly pushed Papyrus off of him and stood up. 

“Yay! Could I get something!?” Papyrus loudly asked as he worked on getting his shoes on. 

“As long as it’s under ten G, then yes Papyrus I will get you something.” Gaster laughed as he watched a beaming Papyrus sprint out of the house before turning to Sans and giving him a small smile, “I understand why you're so tense but you don’t need to worry, if I wished for you dead or kidnapped, I would have done it already. Besides you need to take better care of yourself because if you die then Papyrus will have no one and neither you nor me want that to even be a possibility. So, be careful okay?” Sans stared at him in shock. He had expected to maybe have a place to stay for the night and never in a million years did he think he would be going to the store with a man more than happy to take Paps to the store and let him get almost anything he wanted and willing to give a random monster he picked off the street good advice. 

“Sure old man, now are we going to go or are we going to let Paps run around for another ten minutes?” Sans said purely to change the conversation but even as Gaster rushed outside to look for Papyrus he was still wondering if that man wasn’t a scientist or something with how much odd sense he made. He gave a sigh and slipped out the door with a small kernel of hope lighting up his soul.


End file.
